1. Field of the Invention
This invention relates to the preparation of novel compounds used for the recovery and purification of metals. More particularly, this invention relates to novel ortho alkenyl/alkyl substituted phenyl oxime compounds prepared from natural product sources and processes for selectively separating and recovering of metals from waste effluents and other such aqueous compositions and mixtures containing copper, gallium or other metal ions.
2. Description of the Related Art
The extraction of metals from minerals and their recovery from aqueous compositions and mixtures containing copper and other metals are important commercial processes.
Several extraction methods have been developed for recovering metals values. Solvent extraction processes for the recovery of metal values have certain well recognized advantages over other recovery methods, and such solvent extraction processes are increasing in number and types of applications.
Fundamental to a successful solvent extraction process for the recovery of metals is the identification of water immiscible composition (combination of compounds which will selectively bind to the metal and a suitable solvent) which will selectively extract the metal from an aqueous solution containing copper, and other metals. A further requirement for a successful metal recovery extraction techniques is an extracting composition having the property such that metal values extracted by the extracting solvent can be recovered from the same using another suitable aqueous phase.
Illustrative of such prior art solvent extraction processes are those described in U.S. Pat. No. 3,967,956 and in United Kingdom Patent No. 20 136 443. In the processes of these patents, palladium is recovered from a mixture of palladium and other platinum group metals through use of an extracting composition containing ortho hydroxy oxime compounds, such as alkyl substituted ortho-hydroxyphenyl oxime compounds. The extracted palladium metal is removed from the extracting solvent by contacting same with a strongly acidic aqueous solution.
This method is generally a useful procedure for recovering certain metals from the extracting solvent because the recovery procedure is pH dependent. With ortho- hydroxy phenyl oxime compounds, the extraction process is dependent on the ionizable nature of the phenolic hydrogen, and in the Cu+2 system is generally believed to follow the following equilibrium in which xe2x80x9cLHxe2x80x9d is the un-ionized oxime: 
In accordance with this invention there is provided a small class of ortho alkenyl/alkyl substituted phenyloxime compounds which are useful in the extraction of copper, gallium and other metals. The compounds of this invention are of the formula: 
where R1=C15H31-n and n=0,2,4,6.
R1 is a mixture of one alkyl and three alkenyl hydrocarbonic radical substitutes localized at the benzenic ring of the substituted phenyl aldoxime. That is, when n=0, R1 is a substituent of the formula C15H31. When n=2, R1 is an alkenyl substituent containing one double bond, represented by the following formula: 
When n=4, R1 is an alkenyl substituent containing two double bonds, represented by the following formula: 
When n=6, R1 is an alkenyl substituent containing three double bonds, represented by the following formula: 
The invention uses mild reaction conditions so that the mixture of R1 substituents referred to above can be made from the cardanol found in cashew nut shell liquid, which contains a mixture of molecules containing, no, one, two and three double bonds in the aliphatic lateral chain.
In addition to the aldehydes produced in accordance with the reaction scheme of this invention as precursors of aldoximes within the scope of this invention, ketones can be made by reacting anacardic acid with organolithium compounds like CH3Li, C2H5Li, C3H7Li and other such organometallic compounds, and then reacted like the aldehydes of this inventions to produce corresponding ketoximes.
Our invention is particularly directed to the extraction of gallium from waste effluents from the processing of aluminum-bearing ores, such as bauxite, in which gallium naturally occurs. The liquid effluent from factories that process bauxite to extract aluminum, commonly called Bayer liquor, contains gallium and other metals. Zinc minerals are also known to contain gallium and may be processed with the oximes of this invention for the extraction of gallium. The oximes of this invention also can be used to extract copper, nickel, silver, palladium, germanium and rare earth elements.
The compounds of this invention are mixtures of the formula: 
wherein R1 is C15H31-n and n is 0, 2, 4 or 6 as described above, and mixtures thereof.
The following compounds are illustrative of compounds within the purview of the generic formula set forth above, all of which can be conveniently prepared by simply selecting appropriate natural products for the use in procedures described here in below:
(2-hydroxy,3-alkyl)phenyl aldoxime;
(2-hydroxy,3-alkenyl)phenyl aldoxime;
(2-hydroxy,4-alkyl)phenyl aldoxime;
(2-hydroxy,4-alkenyl)phenyl aldoxime;
(2-hydroxy,5-alkyl)phenyl aldoxime;
(2-hydroxy,5-alkenyl)phenyl aldoxime;
(2-hydroxy,6-alkyl)phenyl aldoxime;
(2-hydroxy,6-alkenyl)phenyl aldoxime.
Particularly preferred are compounds of the above referenced generic formula in which n is 0 and R1 is straight chain alkyl having 15 carbon atoms; n is 2 and R1 is straight chain alkyl having 15 carbon atoms and one double bond between the 8- and 9-carbons; n is 4 and R1 is straight chain alkyl having 15 carbon atoms and two double bonds between the 8- and 9-carbons and the 11- and 12-carbons 11 and 12; and n is 6 and R1 is straight chain alkyl having 15 carbon atoms and three double bonds between the 8- and 9-carbons, the 11-and 12-carbons and the 14- and 15-carbons.
The compounds of this invention can be conveniently prepared by a variety of methods. One preferred method for preparing the compounds of this invention is illustrated in the following Reaction Scheme A: 
Cashew nut shell liquid natural alkylated phenols are used as starting materials to obtain aldehyde intermediates are submitted to reaction with hydroxylamine to produce corresponding aldoximes.
It is known that cardanol is present in cashew nut shell liquid, in concentrations of 5 to 10%, weight by weight, as mentioned in the literature. On the other hand, it is also known that heating cashew nut shell liquid between 180 to 200xc2x0 C., promotes the decarboxylation of anacardic acid, its main component, transforming it into cardanol. Fractional distillation under reduced pressure, at temperature of 200xc2x0 C. and 10-25 mm Hg, produces cardanol in yields up to 65% in weight, relative to the cashew nut shell liquid. This cardanol is a mixture of saturated cardanol and unsaturated cardanols as disclosed above.
On the laboratory scale, cashew nut shell liquid was distilled under reduced pressure (10-25 mm Hg), at temperatures in the range of 200 to 230xc2x0 C. In a round bottom glass flask reaction with three necks, adapted to a refluxer condenser, addition funnels with pressure equalizer and magnetic stirrer, were added, under an inert atmosphere (N2), 45 g of chloroform and 100 g of cardanol mixture distilled from cashew nut shell liquid. The system was heated and 300 mL of a 4.6N sodium hydroxide solution was added drop by drop, keeping on stirring and refluxing for six hours and thirty minutes, at 65xc2x0 C. After reaction, the system is allowed to cool at room temperature.
Pure hydrochloric acid was added to the reaction mixture until a pH of 1 was reached. The purpose of this reduction in pH is to improve the yield of the reaction, transforming the by-product acetals in salicylaldehyde, and also promoting a good separation of organic and aqueous phases.
The organic layer was separated from the aqueous layer by simple decantation, using a separating funnel. 25 g of hydroxylamine hydrochloride dissolved in 50 mL of water was added to the organic layer, keeping the system at 65xc2x0 C. under agitation, for three hours and thirty minutes. The organic layer was separated from the aqueous layer by decantation. The product was purified by extraction with isopropyl ether and concentrated by evaporation of the solvent. These reaction conditions are such as not to reduce the oximes produced from the mixture of cardanols of this invention to a single oxime, but instead produce a mixture of oximes, either aldoximes or ketoximes as desired, that corresponds to the mixture of cardanols isolated from the natural cashew nut shell liquid.
The complexation capacity of this new extractant, can be exemplified by starting from a solution of copper sulphate of known concentration, a reaction with the oximes was carried on; immediately after reaction, the copper remaining in solution is measured by titration.
The procedure is as follows: Weigh 1 g of oximes. Solubilize them totally, using as small a volume of amyl alcohol as possible. In a separating funnel, add 18 ml of CuSO4 (5 g/L) and mix thoroughly. Let the layers separate and discard the aqueous layer. To the organic layer which contains the extractant and the extracted Cu2+, add 14.0 mL of H2SO4, 1:4 v/v to extract the Cu2+ back to the aqueous phase.
The aqueous layer is transferred to a beaker, deonized water is added (approximately 50 mL) and the solution is neutralized with concentrated NH4OH and an excess is added to solubilize all of the Cu2+ as cupric amino complex. After this , the solution is transferred to a glass graduated cylinder and the final volume is reported. A sample of 10.0 mL is transferred to an Erlenmeyer flask and the Cu+2 is titrated with standard 0.001N EDTA solution, using murexide as indicator.
During the experimental trials, it was noticed that during of the carbonylation reaction of the cardanol mixture, using the classic Reimer-Tiemann reaction, very often emulsions were formed during the addition of the solution of NaOH to the reaction medium constituted of chloroform and cashew nut shell liquid.
It was also considered that the double bonds of the alkenyl substituents present in the mixture of the oximes obtained were probably the sites where the hydration reaction could be carried on simultaneously with carbonylation of the benzenic ring.
To solve the problem of emulsion formation, the double bonds were saturated by hydrogenation of the cashew nut shell liquid before reaction. The aim was to eliminate or reduce the possibility of emulsion formation.
Alternatively, the compounds of the invention can be prepared by a variation of the procedure of Reaction Scheme A, which is depicted in Reaction Scheme B: 
After the hydrogenation reaction, the catalyst C/Pd was filtered using diatomite powder to clarify the product. The filtration was conducted in Buchner, under reduced pressure at temperature in the range of 40-45xc2x0 C. The hydrogenated cardanol after cooling down to room temperature, becomes solid around 28-30xc2x0 C., in agreement with the literature.
The product was characterized as a hydrogenated cardanol by its Refraction Index and by Infrared spectroscopy.
During the trials it was observed that the occurrence of emulsions was greatly reduced, making the operating tasks easier.
After the reactions, according to Scheme B, there were carried on the same reactions of carbonylation and oximation as per the following Scheme A: 
The hydrogenation reaction was carried on in a Parr reactor, setting the operational conditions as following: temperature 200xc2x0 C., time 2 hours 50 minutes, speed of mechanical stirrer in the range of 800-1200 rpm. The aldoxime obtained was evaluated as for its capacity of complexing Cu+2, using the same method as used for the mixture of oximes produced as per Scheme A.
The process of Reaction Schemes A and B can be conducted in a batch fashion. The reactants and reagents may be initially introduced into the reaction zone batchwise and either intermittently or continuously into the reaction zone during the course of the reaction. The addition of NaOH solution into the reaction vessel during the Reimer-Tiemann reaction is an example of this procedure.
The following specific examples are presented to more particularly illustrate the invention.